Is underfill really reworkable - I know rework may be feasible, but let's be honest about the detrimental effects of the thermal effect and contamination of a site where underfill was applied, cured, heated and mechanically/chemically removed. I welcome comment - our assemblies are too expensive to scrap out. Any personal experience with any loctite or other "reworkable" undefilled - I rank "reworkable" up there with "washable, but not soluble". -----Original Message----- From: [log in to unmask] [mailto:[log in to unmask]] Sent: Tuesday, May 14, 2002 8:01 PM To: [log in to unmask] Subject: Re: [TN] BGA's on ruggedized assemblies... Our Rockwell friends, through the fumes of Mountain Dew and Coke, will say "No" if your attachment processes are good enough. Personally, though, after some early (low level) vibration failures with some third party designed and assembled boards, I built some more to my own spec and introduced underfilling as an insurance policy. I hope to be able to vibration qual test boards with and without underfilling to see if this process is really necessary. To answer your question, it depends .... on your processes, the operating conditions and expected life of the product, and maybe even the board and BGA materials. Underfill manufacturers claim that using underfill can improve the fatigue life of BGA solder joints by a factor between 3 and 5, but it is another process and it involves heating boards an extra time (if you use the capillary action type underfill) to carry out the underfill process and cure the material. The no-flow type is applied and cured concurrently with the assembly of the BGA onto the board and doesn't involve the extra thermal excursion. I recommend you try qualifying boards with underfill and without it to see if you need the extra process. Underfilling is not necessary in all situations, nor a recommendation, but it won't do any harm either if you want to use it anyway. Peter [log in to unmask] 15/05/2002 05:08 AM Sent by: TechNet <[log in to unmask]> Please respond to "TechNet E-Mail Forum."; Please respond to SteveZeva To: [log in to unmask] cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group) Subject: [TN] BGA's on ruggedized assemblies... Hi All! Gotta question, when BGA's are used on ruggedized assemblies (at least Level-4, probably Level-5), is underfilling BGA's recommended, or a necessity? Thanks, as always... -Steve Gregory- [This e-mail is confidential and may also be privileged. If you are not the intended recipient, please delete it and notify us immediately; you should not copy or use it for any purpose, nor disclose its contents to any other person. Thank you.] ---------------------------------------------------------------------------- ----- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------